The present electronic fuel injection apparatus by BOSCH employs a rotary electromagnetic pump disposed in the fuel tank to feed fuel to the high-pressure passage wherein the fuel pressure is adjusted before it is introduced to the nozzle; thereafter the pressurized fuel is injected into the intake manifold in metered quantities between specified intervals under the control of the electronic control unit (ECU). When applied on compact high-speed engines such as those installed on motorcycles, the above-described fuel injection apparatus presents the problems of high cost, low reliability and severe fluctuation of intake pressure.
A new type of pulse electromagnetic fuel injection device disclosed in a Chinese patent publication No. CN1133810C entitled “Electronically Operated Fuel Injection Device” comprises a fuel intake member, a fuel driving member and a fuel injector; the magnetic flux generated by the actuating solenoid and the resetting solenoid of the fuel driving member drives the driven member which consists of an armature core and a plunger to achieve the circulation of fuel suction and fuel injection. The integrated fuel feed device provided in the aforesaid invention sucks fuel directly from the fuel tank via the low-pressure passage.
In actual applications, the integrated fuel feed devices may encounter certain problems such as strict installation manner, long standby time, hot restarting, long-time idling operation and high-load running under high temperature, and thereby the fuel vapor generated in the inner and outer passages thereof may severely disturb the normal fuel feed operation. Therefore a more preferable embodiment wherein the generation of fuel vapor can be restrained and further the generated fuel vapor can be timely discharged is imperative.
Another Chinese patent publication No. CN1474910A entitled “Electronically Controlled Fuel Injection System” particularly emphasizes the possibility of the aforesaid problems; thereby it installs a by-pass passage from the admission port of the intake passage to the outlet of the return passage between the solenoid and the cylinder to directly introduce the fuel back to the fuel tank. But it is still very possible that the fuel vapor would accumulate inside and outside the fuel feed device thereby to disturb the normal operation thereof because of certain problems such as the relatively stationary state of the constitution wherethrough the return flow passes, the lack of enough driving power and the over-sensitivity thereof to the installation manner. Based on the aforesaid patents, a third improved Chinese patent publication No. CN1458403A entitled “Electronically Controlled Fuel Injection Unit” preserves the return passage and further adds a check valve at the drain port thereof to prevent the fuel vapor from entering the pressure chamber.
The patents or patent applications mentioned above do not provide any mechanism to actively prevent the generation of fuel vapor and the driving power to discharge the generated fuel vapor, and still further the devices provided therein require strict installation manners, which actually keep them from completely eliminating the aforesaid problems.